Continuous process for recovering bromine from sea water and the like



Nov. 1, 1932. J. J. GREBE ET AL 1,885,255

CONTINUOUS PROCESS FOR RECGVERING BROMINE FROM SEA WATER AND THE LIKE Filed July 2. 1930 Patentdd New. 1, 1932 l a I 1. =1

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; e a a lication and July a aeol Semarang arser Thelpresent invention is concerned with improvements n methods for extract ng bromine from natural waters and other saline solutions, and has particular regardato a conbromme dllr tinuous process for recovering rectly from sea water and obtaining the same as liquid bromine without necessity for-preconcentruting said sea water, "as by solar evaporation. y We have found that brom1ne, whe n liberated from sea water on like solutions of extremely low bromine content by oxidizing the acidified solution with chlorine or by equivalent means, may be removed from the solution by blowing-out with a current of air and that all of the bromine so removed may then be absorbed from the bromine-laden air by passage through a bed or body of active carbon or charcoal. The bromine-saturated charcoal may then be heated or steamed to vaporize and separate the bromine, along with some hydrobromic acid, and such reliberated bromine may be condensed directly as liquid bromine, whilethe aqueous distillate may be treated with chlorine equivalent to the hydrobromic acid therein, and the so treated distillate redistilled to recover liquid bromine therefrom. It is among the objects of the invention to provide a continuous, in-

terconnected process of the aforesaid general character whereby liquid bromine ma produced directly from sea water an the r i like by oxidizing underappropriate conditions without having recourse to any preliminary concentration or to heating the solu tion, and without employing any step involving absorption of bromine vapors by an alkali. Other objects and advantages will appear as the description proceeds. The invention, then, consists of the ste s hereinafter full described and particular y pointed out in the claims, the following description and accompanying drawing setting forth in detail but a few ofthe variousways in which the principle of the invention may be used.

Referring to the drawing, the single figure is a diagrammatic representation of an a paratus layout adapted for carrying out t e process of the invention. I Sea water, or other solution ,from which bromine is to be extractcurrent.

ed, is received ina cistern 1 and is'forwarded bromine. In the upper sectionof tower 4 the intermixin of chlorine with the solution takes place, while in the lower section the reaction for the liberation of bromine is completed, the rate of flow of solution over the tower being sh adjusted to the height and capacitythcrcof that all of the bromine will I have been liberated when the treated solution leaves the tower through trapped outlet pipe 7. The bromine solution flowsthrou 11 pipe 7 to a distributor 8', hereshown as of t he weir type, located at the topof blowing-out tower 9 also filled with a suitable packingsupported upon grid 10. Thesolutioncflows downwardly in istributed manner over the packing in tower 2- against an ascending voluminous current ofair introduced into the basevllof tower 9 by means of duct 12 and blower 13, whereby the bromine may be substan ally completely removed or blown out of the olution in the manner well known in the art, such bromine being carried ,awa by the air The debrominated e uent flows from the tower base 11 through a waste pipe 1 1iv rovided with a liguidseal, e. g. as shown.

he bromine-laden .air leaves tower 9 through exit passage 15, in which may be disposed aseriesqf bafile plates 16 for arresting spray carried over from the tower, and passes thence through oneor mol e llayers or beds of active charcoal. One convenient arrangement thereof, as illustrated, provides one or more carbon containers or absorbers 17 consising of a series Of vertically spaced inclined plates or louvers, ,ntoeach absorber,

granular charcoalis chargedthrough a hopby gravity and filling the space between the louvers to a degree governed more or less by the angle of repose of the free flowing material, thereby forming a continuous column of charcoal through which the current of bromine-laden air is drawn in a lateral direction by means of the suction of blower 13 acting through duct 19. When the charcoal becomes saturated with bromine, it is discharged by opening valve 20 into a conveyor 21 which removes the charcoal to the bromine recovery apparatus described below. By employing two or more of the charcoal units continuous operation of the system may be maintained, since, while the charcoal from one such unit is being discharged and the unit refilled, the remaining units continue to function, and no interruption of the fiow of the air current is necessitated. Other means of contactin the bromine-laden air current with the adsor ent material, however, may be employed, the one shown in the foregoing description being illustrative of one way of accomplishing the result, but not intended as a limitation upon the invention.

As is evident from the foregoing description, the volume air is continuously recirculated through the system, blowing out the bromine in the tower 9 and being stripped of the bromine vapors in the absorbers 17. Therefore, while complete absorption of bromine vapors may be readily accomplished by properly proportioning the capacity of absorbers to the volume of air flow, any bromine escaping absorption is returned to the system with the recirculated air.

The bromine-saturated charcoal discharged from absorbers 17 is conveyed by conveyor 21 to a steaming out column 22 consisting of a vertical cylindrical chamber, conveyor 21 discharging thereinto at a point below the upper end of the column so that the body of charcoal fills the lower portion thereof leaving a vapor space in the upper portion. Steam is admitted at an inlet 23 and passes upwardly through the body of saturated charcoal, heating the latter and driving all the bromine. The debrominated charcoal is discharged from the base of column 22, a mechanical discharger 24 being shown therefor, and may be returned for reuse in the absorbers 17.

The mixture of bromine and water vapor, containing some hydrobromic acid, leaves column 22 through outlet passage 25 and is conducted to a condenser 26, which may consist of a water-cooled ceramic coil, wherein the vapors are condensed. The liquid condensate flows into a separator 27 wherein two la ers are formed, the lower layer consisting 0 liquid bromine and the up er layer an aqueous solution of bromine and ydrobromic acid. Liquid bromine is withdrawn through draw-elf 28 while the aqueous layer overflows through pipe 29 and is conducted to a treating column 30 for the recovery of bromine therefrom. Column 30 contains an acidproof packing over which the solution flows. At a point about midway of the column chlorine is admitted through inlet 31, while steam is admitted at inlet 32 located at a lower tpoint. The chlorine liberates bromine from c aqueous hydrobromic acid solution, and such bromine together with that already dissolved in the solution is boiled or steamed out, the va ors being returned through pipe 33 to con enser 26. A solution of hydrochloric acid is discharged from column 30 through trapped discharge pipe 34 and flows to cistern 1, wherein it is mixed with the raw sea water and serves to neutralize partially the alkalinity thereof, thus reducing the acid requirements to be added at 5 by an equivalent amount.

When operating the herein described system the sea water, if such be used as the source of bromine, containing about parts bromine per million, is first acidified to establish a suflicient hydrogen ion concentration therein to enable the liberation of all of the bromine. We have found that a degree of acidity represented by a pH value between 6 and 6.5 is necessary in order to liberate all of the bromine in the elemental state, although a greater acidity, e. corresponding to a pH value as low asp =3 or lower, ma. be employed without other detriment than he extra cost of the acid consumed. For the acidification, a strong mineral acid, e. g. sulphuric, hydrochloric or nitric acid, is preferably employed. The addition of acid may be correlated for urposes of controlling the operation with an indicating instrument to show the hydrogen ion concentration of the acidified mixture, such control being desirably made automatic by means responsive to the hydrogen ion indication.

The sea water, or equivalent solution, having been acidified to a pH value between about 6 and 3, is then treated in chlorinator 4 with sulficient chlorine to liberate all of the bromine therein. A material excess of chlorine is advantageously to be avoided, as such excess accompanies the bromine through the subsequent process steps and must be separated therefrom in order to yield a pure final product. An excess of chlorine may also cause over-oxidation of some of the bromine initially liberated, especially when working with solutions near theupper H limit, i. e'. pH=6, forming thereby solu le bromine compounds which go into solution and thus esca extraction. The last-mentioned condition is more particularly exlained in our co-pending application Serial 0. 472,027, filed July 31, 1930, in which an electrometric method for controllin the chlorination is described and claime In general, however, the amount of chlorine used should not be more than about 30 per cent in excess of that theoretically required liberate all of the bromine although it is desirable to reduce the excess to a lower figure, when practical by employm accurate control means for determining directly, the degree of. chlorination. The chlonnatmg operation is preferably carried out without heating the water, althoughheat ma be added in this step without departing om the scope of the invention. Instead o treating with chlorine in this step, equivalent means for oxidizing the solution to liberate bromine in the essential state may be employed, such as electrolyzin or treating with other known chemical oxi Zing agents.

The removal of free bromine in lowingout tower 9 is accomplished in the manner old in the art, for instance as originally dzsclosed in U. S. Patent 460,370 to Herbert H. Dowj For the purpose a large volume of air at low pressure, e. about 2 to 8 inches water column, is emp oyed. B suitably proportioning the flow of aci ified and chlorinated solution in the tower to the volume of air andto the height and cross-section of the tower, the bromine may be substantiall completely blown out of the solution so that an analysis of the eflluent from the base of the tower shows a bromine content as low as 1 to 5 parts per million. The bromine-laden air leaving tower 9 passes first through a spray arrester and is then intimately contacted with a body of active charcoal in any suitable manner, the means therefor previously described having been found especial] advantageous for quickness and case of c arging fresh charcoal and discharging saturated charcoal, as well as for exposing a relatively large surface thereof to contact with the air current. A granular form of charcoal of about 10 to 20 mesh size, and havin sufiicient hardness to withstand mechanical handling without excessive crumbling and dusting, is preferred, such as oocoanut charcoal. Other forms of active carbon or other solid materials capable of adsorbin bromine, such as silica gel or similar metallic oxide gels, may also be used, but

in some cases less desirably. We have found that charcoal adsorbs bromine from moist air without lldSOIblIl" an appreclable amount of water, whereas silica gel adsorbs Water aswell as bromine and becomes saturated with a much lower total bromine content thanin the case of active charcoal. The charcoal may be used repeatedly and apparently loses nothin in effectiveness for adsorbing bromine, iiut some mechanical loss thereof occurs due to attrition in handling. It is preferable to separate the dust from the granular mass by screening or by air flotation before charging the same into the absorbers.

When fresh charcoal is employed we have found that a large proportion of the bromine adsorbed, i. e. as much as 20 to 40 per cent, may be converted to h drobromic acid when the saturatedcharcoa is steamed out. As the charcoal is used over and over again, however, the proportion of bromine so converted becomes pro essively less, and after a few repetitions 0 use of the charcoal the amount of h drobromic acid formed in steaming out t e bromine therefrom may be rcduced to a very small, even almost no liglble, fi It is thought that this be avior is ue to the hydrogen originally held occluded by the charcoa due to its method of preparation, and that when such h drogen has been reacted there is little i an nrther formation thereof in connection wit the o ration of the present process. Since the b owing-out and absorption of bromine takes place at'about ordinary temperature, varym only with the temperature of the atmosp ere and of the water entering the process, there can be little or no catalytic decomposition of moisture to form hydrogen accompanying the aforesaid process steps. In t e steaming-out step the bromine-saturated charcoal, containing about 15 to per cent of its weight of bromine, may be pletely separated from the bromine with a steam consumption of about 3 to 4 pounds or less per pound of bromine, using saturated steam at about 5 pounds pressure. Other means of heating t e saturated charcoal to remove bromine therefrom may be em loyed, such asb means of hot air or com ustion gases, or y external heatin but the use of steam for the purpose aiior obvious advanta es.

The liquid bromine condensed and collected in separator 27 contains some chlorine as impurity, the amount of the latter dependin upon the control of the chlorination an hence the. excess of chlorine used therein. With accurate control the percentage of chlorine in the bromine, roduct should not exceed 1 to?) per cent. T e purification of the liquid bromine may be carried out by any of the well-known methods, such as by treatment with an aqueous bromide solution.

The water layerdrawn off from separator 27 is approximately saturated with bromine and also contains whatever hydrobromic acid is formed in the steaming-out step. This solution is treated in column 30 with sufficient chlorine to liberate the bromine from such hydrobromic acid, and the total free bromine therein is simultaneously steamed out and returned to the condenser 26. The addition of chlorine may be controlled by any suitable means, such as already suggested for the initial chlorination of the acidified sea water. The eliluent from column 30 is an aqueous hydrochloric acid solution, which is most economioally employed for acidifying the raw sea water in custom 1.

It will be seen accordingly, that the novel process hereinbefore descri ed in detail opercomates with a minimum consumption of raw materials and under pro er control is capable of recovering substantia ly all of the bromine contained in sea water in a continuous c cle of steps the product of which is liqu d romine. At only one fpoint in the process is there a possibility o bromine values'being lost, that being in the eflluent discharged from blowing-out tower 9. It has been found however, that the total bromine content oi such eflluent can be held to 5 parts bromine per million or less with economical working which does not demand excessive power consumption for the blowing-out operation. At all other points in the system the gases, solutions or solids from which bromine has been extracted are returned to the process cycle and any bromine values contained therein are retained in the system. The invention, however, is not limited to condensin the bromine vapors, when driven oil from e adsorbent material by heating the latter, as liquid bromine, but also comprehends absorbing such vapors in a liquid medium, such as an alkaline solution or an organic solvent, if so desired.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the process herein disclosed, provided the step or steps stated by any of the following clauns or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention 1. The process of recovering bromine which comprises contactin a current of bromineladen air with a be y of active charcoal to adsorb bromine thereon, heating such charcoal with steam to distill the bromine therefrom, condensing the vapors of water and bromine and separating l1 uid bromine from the a ueous solution there y obtained.

2. The process of recovering bromine which comprises contacting a current of bromineladen air with a body of active charcoal to adsorb bromine thereon, heating such charcoal with steam to distill the bromine therefrom, condensing the va ors of water and bromine, separating liqui bromine from the aqueous distillate containing h drobromic acid, treating the latter with ch orine suflicientto liberate bromine therefrom, vaporizing the so liberated bromine and returning the vapors to the condensing step.

3. The continuous process of extracting bromine from sea water and the like which comprises acidifying the same, treating with chlorine to liberate bromine therein, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of adsorbent material and heatifng such adsorbent to separate bromine thererom.

4. The continuous process of extracting bromine from sea water and the like which comprises aeidifyin the same, treating with chlorine to liberate romine therein, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, heating such charcoal with steam to vaporize bromine therefrom, condensing the vapors and se arating liquid bromine from the aqueous istillate.

5. The continuous process of extractin bromine from sea water and the like which comprises acidifying the same, treating with chlorine to liberate bromine therein, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, heatin such charcoal with steam to vaporize bromine therefrom, condensing the vapors, separating liquid bromine from the a ueous distillate containing hydrobromic aci treating the latter with chlorine to liberate bromine therefrom, d'stilling ofi such bromine with steam, returning the vapors to the condensing step and employing the residual aqueous hydrochloric acid solution for acidifying more raw sea water.

6. The continuous process of extracting bromine from sea water and the like which comprises acidifyin the same, oxidizing to liberate bromine in t 1e elemental state, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of adsorbent material and heatin such adsorbent to recover bromine there rom.

7. The continuous process of extracting bromine from sea water and the like which comprises acidifyin the same, oxidizin to liberate bromine in the elemental state, b owing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, heating such charcoal with steam to vaporize bromine therefrom, condensin the vapors and separating liquid bromine rom the aqueous distillate.

8. The continuous process of extractin bromine from sea water and the like whic comprises acidifying the same, oxidizing to liberate bromine in the elemental state, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, heating such charcoal with steam to vaporize bromine therefrom, condensing the vapors, separating liquid bromine from the aqueous distillate containing hydrobromic acid, treating the latter with chlorine to liberate bromine therefrom, distilling ofi such bromine with steam, returning the vapors to the condensing step and employing the residual a ueous hydrochloric acid solution for acidifying more raw sea water.

9. The process of recovering bromine which comprises contactin a current of bromine-laden air with a ho y of an adsorbent material of the class consisting of active carbon, active charcoal, and a metallic oxide gel, heating the bromine-charged adsorbent material with steam to distill the bromine therefrom, condensing the vapors of water and bromine and separating liquid bromine from the aqueous solution thereby obtained.

10. The continuous process of extracting bromine from sea water and the like which comprises acidifying the same, treating with chlorine to liberate bromine therein, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, recycling the debrominated air to said blowingout step, heating the bromine-charged charcoal with steam to vaporize bromine therefrom, condensing the vapors, separating liquid bromine from the aqueous distillate containing hydrobromic acid, treating the latter with chlorine to liberate bromine therefrom, distilling off such bromine with steam, returning the vapors to the condensing step and employing the residual aqueous hydrochloric acid solution for acidifying more raw sea water.

11. In a process of recovering bromine, the steps which consist in contacting a current of bromine-laden air with a body of adsorbent material to remove bromine therefrom by adsorption on such material, then heating such bromine-charged material to vaporize bromine therefrom and condensing the vapors.

12. In a process of recovering bromine, the steps which consist in contacting a current of bromine-laden air with a body of active charcoal to remove the bromine therefrom by adsorption on such charcoal, then heating such bromine-charged charcoal to vaporize bromine therefrom and condensin the vapors.

Signed by us this 30 day 0 June 1930.

JOHN J. GREBE. RAY H. BOUNDY.

CERTIFICATE OF CORRECTION.

Patent No. 1,885,255. November I, 1932.

JOHN J. GREBE ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 8, for "said" read "such"; page 3, line 13. for "essential" read"elemental"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed-and sealed this 10th day of January, A. D. 1933.

(Seal) Acting fiooiiiiisstone'fbf Patents.

which comprises contactin a current of bromine-laden air with a ho y of an adsorbent material of the class consisting of active carbon, active charcoal, and a metallic oxide gel, heating the bromine-charged adsorbent material with steam to distill the bromine therefrom, condensing the vapors of water and bromine and separating liquid bromine from the aqueous solution thereby obtained.

10. The continuous process of extracting bromine from sea water and the like which comprises acidifying the same, treating with chlorine to liberate bromine therein, blowing out the bromine with a current of air, removing bromine from such air current by contact with a body of active charcoal, recycling the debrominated air to said blowingout step, heating the bromine-charged charcoal with steam to vaporize bromine therefrom, condensing the vapors, separating liquid bromine from the aqueous distillate containing hydrobromic acid, treating the latter with chlorine to liberate bromine therefrom, distilling off such bromine with steam, returning the vapors to the condensing step and employing the residual aqueous hydrochloric acid solution for acidifying more raw sea water.

11. In a process of recovering bromine, the steps which consist in contacting a current of bromine-laden air with a body of adsorbent material to remove bromine therefrom by adsorption on such material, then heating such bromine-charged material to vaporize bromine therefrom and condensing the vapors.

12. In a process of recovering bromine, the steps which consist in contacting a current of bromine-laden air with a body of active charcoal to remove the bromine therefrom by adsorption on such charcoal, then heating such bromine-charged charcoal to vaporize bromine therefrom and condensin the vapors.

Signed by us this 30 day 0 June 1930.

JOHN J. GREBE. RAY H. BOUNDY.

CERTIFICATE OF CORRECTION.

Patent No. 1,885,255. November I, 1932.

JOHN J. GREBE ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 8, for "said" read "such"; page 3, line 13. for "essential" read"elemental"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed-and sealed this 10th day of January, A. D. 1933.

(Seal) Acting fiooiiiiisstone'fbf Patents. 

